1. Field of the Invention
This invention relates to two-pin electromagnetic flasher switches which can be utilized in automotive applications.
2. Background of the Invention
Flasher switches of various designs have been made in the past each of which have certain inherent disadvantages. Thermal flasher switches incorporating a bi-metal construction designed to be activated upon resistance heating and expansion of metal components continue to be in frequent use. Such units are popular due to relatively low cost of manufacture. Other disadvantages such as temperature sensitivity and limited lifespan make thermal switches less favourable in a wide variety of heavy duty applications such as in trucks. Other flasher switches of the electro-mechanical type, including the switch disclosed in U.S. Pat. No. 3,611,288, incorporate a number of moving parts, are generally heavy and are relatively costly to manufacture and suffer from other disadvantages.
Flasher switches of known design incorporating single throw relays have generally been of two basic designs, that is, having either a two-pin or three-pin configuration. Similarly, such flasher switches have been designed for operation under either fixed load or variable load conditions. These known flasher switches were not suitable for or capable of being readily adapted for use in such differing applications without substantially adversely affecting cost and size considerations.
Flasher switch designs of the two pin type are commonly used in heavy duty applications in heavy transportation and construction vehicles such as trucks. Many original equipment manufacturers (OEM's) have specified flasher switches of the two-pin type On the otherhand, although many passenger car OEM's have featured three pin flasher switches, there is a demand for two pin flashers which may be used for after market replacement of failed original equipment of the three-pin type.
Flasher switches designed for fixed load applications, particularly for use in connection with turn signal circuits, when used in connection with multiple lamps, typically indicate an outage by maintaining the circuit in the closed position and continuously lighting all remaining operative lamps. In passenger cars for example, upon failure of one or more turn signal lamps, there is a lowering of the load on the flasher switch circuit which prevents the relay component of the flasher switch from being activated to commence flashing of the remaining turn signal lamps.
Variable load flasher switches are commonly used in hazard warning light circuits in passenger car motor vehicles and heavy trucks. Generally, it is essential that hazard warning lights be capable of operation even if one or more lamps operated on the circuit have failed. Similarly, manufacturers and operators of heavy-duty vehicles such as trucks commonly specify variable load flashing switches which are capable of operating turn signals even where one or more lamps are inoperative without significantly adversely affecting the flashing or cycling frequency of the remaining lamps In applications involving trucks, it is not uncommon for as many as 16 lams to be operated on each of both turn signal circuits.
Other design parameters for flashers are typically specified by OEM's and those parameters are indeed important in the selection of suitable flasher switches to meet those requirements. One such parameter is the maximum elapsed time of operation of the switch from activation to the time of the first flash of the lamps in operation. It is generally desirable that the flasher switch exhibit a relatively low elapsed time to the first flash to increase visibility under high speed operation on highways and the like. A second important parameter is the frequency of flashing which also must be maintained within a specified range. Frequencies which are either too low or too high make the flasher switches undesirable for use. A third factor is the percentage of time on during duty cycle which is a measure of the time that the lamps remain lighted during a full cycle. Other important design parameters are the durability of the switches, including the number of cycles expected under normal operating conditions and resistance to shock and dirt damage.
The audibility of a flasher switch during operation is also a relatively important design parameter. Operators of noisy, heavy equipment, and passenger cars, find it desirable if the flasher switch generates a relatively loud noise sufficient to be audible over a range of wind noise, engine and other noises encountered during vehicle operation.
Flashers developed for after-market installation in older vehicles have typically incorporated 2 pin configurations. Flasher assembles of the 3 pin type could not be readily installed in such older vehicles without first making modifications to other existing vehicle components.
In the prior art, electronic flashers have heretofore incorporated 3 pin configurations, the third pin being a ground pin. According to the present invention, a two pin electronic flasher assembly is provided which may be readily incorporated into new, original vehicle applications and into after market installations. Electronic flashers of the present invention may be adapted to fit existing receptacles having 2 pin or 3 pin flasher configurations as the need for a third ground pin has been eliminated.